This project is comprised of research into the structure and function of ion transport systems. There are currently three active subprojects: 1) Transient kinetics: A collaborative study with Froehlich and Fendler. The source of the transmembrane current that is generated by phosphorylation of the sodium pump has been identified as either the major conformational transition or the dissociation of Na+ that immediately succeeds this event, 2) Studies of the sodium selectivity of different stages of the sodium pump mechanism. Steady-state phosphorylation kinetics have been employed to identify a role for Mg2+ in establishing the sodium selectivity of the ionophoric domain of the sodium pump and to correlate this with the conformational state of the pump; and 3) Expression and localization of sodium pump isoforms in the nervous system. A study of the regulation and expression of isoforms of the Na,K- ATPase utilizing oligonucleotides and site-directed antibodies (raised against synthetic peptides as identifying probes.